Reference Guide

768 | sFlow
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Figure 43-1. sFlow Traffic Monitoring System
Implementation Information
Dell Networking’s sFlow is designed so that the hardware sampling rate is per line card port-pipe and is
decided based upon all the ports in that port-pipe. If you do not enable sFlow is not enabled on a specific
port, the global sampling rate is downloaded to that port and calculates the port-pipe’s lowest sampling
rate. This design supports, the possibility that sFlow can be configured on that port in the future. Back-off
is triggered based on the port-pipe’s hardware sampling rate.
For example, if port 1 in a the port-pipe has sFlow configured with a 16384 sampling rate while port 2 in
the port-pipe has sFlow configured but with no sampling rate set, FTOS applies a global sampling rate of
512 to port 2. The hardware sampling rate on the port-pipe is ten set at 512 because that is the lowest
configured rate on the port-pipe. When a high traffic situation occurs, a back-off is triggered and the
hardware sampling rate is backed-off from 512 to 1024. Note that port 1 maintains its sampling rate of
16384; port 1 is unaffected because it maintain the configured sampling rate of 16384.
To avoid the back-off, either increase the global sampling rate or configure all the line card ports with the
desired sampling rate even if some ports have no sFlow configured.
Important Points to Remember
• The FTOS implementation of the sFlow management information base (MIB) supports sFlow
configuration via the
snmpset command.
• Dell Networking recommends that you connect the sFlow Collector be connected to the Dell
Networking chassis through a line card port rather than the route processor module (RPM)
Management Ethernet port.
• S-Series sFlow sampling is done on a per-port basis.
sFlow Collector
sFlow Agent
Switch/Router
Switch ASIC
sFlow Datagrams
Poll Interface
Counters
Interface
Counters
Flow Samples